1. Field of Invention
This invention relates to masks that assist respiration.
2. Background
Obstructive Sleep Apnea (OSA) is intermittent blockage of a person's airflow while they sleep due to movement of their tongue or other soft tissue. Such blockages can happen hundreds of times each night, causing poor sleep and oxygen deprivation. Basically, the person temporarily stops breathing during each blockage. Unfortunately, the person might not even be aware of this serious problem because they never fully wake up during blockages.
Obstructive sleep apnea can cause serious long-term harmful effects. These harmful effects include: disrupted sleep; chronic fatigue; morning headaches; irritability; brain damage; cognitive dysfunction; impotency; high blood pressure; heart attacks; congestive heart failure; motor vehicle crashes; job-site accidents; and even death. Despite these harmful effects, it is estimated that only 5% to 8% of the affected population are treated. Approximately 20 million Americans and 35 million people worldwide have obstructive sleep apnea and the number is growing rapidly.
The first-line therapy for most people who are diagnosed with obstructive sleep apnea is Continuous Positive Airway Pressure (CPAP). CPAP keeps the airway open with a stream of pressurized air that is channeled into a person's nose (or nose and mouth) while they sleep. The positive pressure keeps their tongue and other soft tissue from blocking the airway. A CPAP machine continuously pumps pressurized air into a CPAP mask that fits over a person's face while they sleep. Some CPAP masks cover only the sleeper's nose. Other CPAP masks cover both the sleeper's nose and mouth.
In many respects, the mask is the weak link of CPAP. CPAP only works if a person tolerates wearing the CPAP mask and if the mask does not leak pressurized air. If the mask fits too tightly in some places where the mask presses against the person's face, then this can cause skin irritation, red marks, and pain. These problems contribute to high non-compliance with CPAP therapy; many people are not willing to wear a CPAP mask while they sleep. Estimates of the percentage of people who should wear CPAP masks but do not wear them range as high as 50%. On the other hand, if the mask fits too loosely and there are gaps in some places between the mask and the person's face, then the mask leaks pressurized air. Air leaks erode the clinical effectiveness of CPAP.
The main challenge for designing a CPAP mask is how to create a mask that closely conforms to the contours of an individual's face while they sleep so that there are no places around the mask that fit too tightly (causing irritation, skin marks, and pain) and no places that fit too loosely (causing air leaks). This challenge is especially difficult because different people can have quite different facial contours. Also, facial tissue contours can change during sleep. For example, facial contours can shift as a person rests their head and face on a pillow, particularly for people who sleep on their side or on their stomach. The ideal CPAP mask should not only be adjustable to custom fit the contours of an individual's face, but should also adjust to changes in that person's facial contours while the person sleeps.
There are various approaches in the prior art that attempt to address this main challenge for CPAP design. These approaches include: masks with adjustable straps; masks whose overall size can be manually adjusted; masks with a cushion seal filled with a gas, liquid, or gel; masks with an inflatable single-compartment cushion seal; masks that are custom fitted for a person's face by pressing moldable material against their face; and masks that are custom fitted for a person's face using three-dimensional facial imaging and custom fabrication. Some prior art combines two or more of these approaches. For example, one can design a mask with both adjustable straps and a gel cushion.
However, none of the approaches in the prior art have solved the main challenge of how to create a CPAP mask that conforms and adapts to the contours of an individual's face while they are wearing the mask. Accordingly, skin irritation from tight places around CPAP mask perimeters and air leaks from loose places around CPAP mask perimeters remain ongoing problems in CPAP therapy. There is still a clinical need for an innovative CPAP mask to correct these problems. This need is met by the invention disclosed herein. This invention can custom fit a CPAP mask to the contours of particular individual's face while the person is wearing the mask, even while they sleep. This invention can achieve uniform pressure on the person's face around the entire perimeter of the mask to reduce skin irritation and air leaks. This can increase patient compliance with CPAP therapy and reduce obstructive sleep apnea's harmful effects.
We now review the five general approaches that have been pursued in the prior art to address these CPAP mask problems and discuss the limitations of each approach. Then we introduce the invention disclosed herein and discuss how it addresses the limitations of these approaches in the prior art.